The chemical and physical characteristics of neurotubules and neurofilaments and their relationship to axonal flow phenomena will be studied in various in vivo and in vitro model systems of rat peripheral nerve. Ultrastructural studies of rat peripheral nerve segments incubated in various media before fixation will be used to study physical properties of these organelles. The loss of neurotubules and neurofilaments under these conditions will be quantitatively correlated with the protein and colchicine-binding activity extracted from the tissues as well as the profile of these proteins obtained from SDS- polyacrylamide gel electrophoresis. Rabbit anti-pig tubulin antisera will also be used to evaluate the tubulin content of these extracted proteins using Ouchtolony and immunoelectrophoretic methodologies. This antisera will also be conjugated with fluorescein isothiocyanate to assess the cellular distribution of tubulin antigens within neural and other tissues. The participatory role of neurofilaments and neurotubules in axonal flow will be studied in an in vitro model system in which alterations of axonal transport phenomena may be correlated with structural changes of these organelles following exposure to neurotoxic substances. Other model systems will be used to study the alterations of neurotubules and neurofilaments during the changes of Wallerian degeneration, particularly as they relate to excessive entry of calcium into the intra-axonal compartment during this phenomenon.